1. Field of the Invention
The present invention generally relates to an image forming apparatus and a method of controlling an image forming apparatus, particularly to control of thermal fixation of a color material.
2. Description of the Related Art
There is a technique of controlling the fixing temperature of a fixing unit in accordance with the amount of applied toner obtained from image data. Japanese Patent Laid-Open No. 2000-242107 (patent literature 1) discloses a method of determining whether input image data is a photographic image or a character image, and when fixing a photographic image, making the fixing temperature of the fixing unit higher than that when fixing a character image. According to patent literature 1, the power consumption of the fixing unit can be reduced by adjusting the fixing temperature in accordance with the amount of applied toner of image data.
An image forming apparatus has a page aggregation function for saving the number of paper sheets to be output. The term “paper aggregation” means printing images of a plurality of pages on one paper sheet (also called N-in-1 or N-up printing). For example, two A4-size images are adjacently formed on an A3-size sheet, or A4-size images are reduced to ½, and images of two pages are formed on one A4-size sheet.
However, when performing page aggregation, the amount of applied toner is derived in each of the images of a plurality of pages as the subject of page aggregation. For this reason, when performing page aggregation of a plurality of pages with different amounts of applied toner, the above-described fixing temperature adjustment according to the amount of applied toner is not appropriately performed.